To make the vinaigrette, whisk lime juice, vinegar, grapefruit juice, honey, salt and pepper in a bowl. While whisking constantly, slowly drizzle in the olive oil.
Place beets in an oven safe dish tossed with 1 tablespoon of the olive oil and the tarragon. Cover with aluminum foil and roast for 2 hours, until tender. Let cool and peel the beets. Slice the beets.
Thinly slice the fennel.
Fry the pancetta until golden brown and crispy. Drain.
Preheat oven to 350 F.
To make the croutons, chop the mini loaf. Toss with the remaining tablespoon of olive oil, salt and pepper.
Place in oven and toast for 15 minutes, until crispy.
Toss the fennel, basil, grapefruit, pancetta and mozzarella with the vinaigrette. Leave for at least 10 minutes to let the foods absorb the flavors of the vinaigrette.
To plate, place sliced beets on the bottom.
Add tossed fennel, etc. on top. Garnish with the croutons.